1. Field of the Invention
The present invention relates to a linear actuator which makes it possible to linearly and reciprocatively move, along a guide rail, a slider assembled integrally with a ball screw shaft.
2. Description of the Related Art
A linear actuator, which is based on the use of such a ball screw shaft, has been hitherto known. For example, both outer surfaces of a slider are movably supported in a major axis direction of both inner surfaces of a guide rail having a substantially U-shaped cross section by the aid of ball rolling members. A ball screw shaft, which is attached to the slider and which is meshed with a ball screw hole, is rotated, and thus the slider is allowed to make reciprocating movement (see Japanese Patent Publication No. 7-61587).
However, in the case of the conventional linear actuator, if the width of the slider is widened while maintaining a constant spacing distance between the both outer surfaces of the slider and the both inner surfaces of the guide rail, the following problem arises. That is, the width of the guide rail is enlarged as a matter of course. As a result, the linear actuator has a large size, and the weight is increased.
A general object of the present invention is to provide a linear actuator which makes it possible to decrease the volume of a guide rail and reduce the weight by providing ball rolling members between both inner surfaces of a slider and both outer surfaces of a guide rail so that the widthwise dimension of the guide rail is set to be small.
A principal object of the present invention is to provide a linear actuator which makes it possible to absorb any discrepancy of parallelism between the axis of a ball screw shaft and the axis of a ball rolling groove by providing and holding a ball screw nut floatably with respect to a slider to enable the ball screw nut to follow the operation form of the ball screw shaft.
The above and other objects, features, and advantages of the present invention will become more apparent from the following description when taken in conjunction with the accompanying drawings in which a preferred embodiment of the present invention is shown by way of illustrative example.